Income Taxes (Narrative) (Details) (USD $)	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2013	Jun. 30, 2013	Sep. 30, 2012
Income Taxes [Line Items]
Taxes refundable to customers		$ 65,069,000	$ 66,392,000
Recoverable future taxes		152,122,000	150,941,000
Tax benefit recorded from exercise of stock options		4,300,000	600,000
Tax Benefit Not Realized Due to Tax Loss Carryforward		33,600,000	32,700,000
Unrecognized tax benefit decrease		9,300,000
Amount of the unrecognized tax benefit decrease that reduced the effective rate	2,100,000
Amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate		2,000,000
Change in unrecognized tax benefits		2,000,000
Deferred Income Taxes [Member]
Income Taxes [Line Items]
Taxes refundable to customers		65,100,000	66,400,000
Recoverable future taxes		$ 152,100,000	$ 150,900,000